研究了在大肠杆菌中克隆和表达来自热泉宏基因组的一个β-半乳糖苷酶基因以及该β-半乳糖苷酶在动物营养中的初步应用。以大理洱源一个65℃热泉微生物宏基因组DNA为模板,克隆得到该基因全序列。根据同源性分析,该β-半乳糖苷酶与Thermotoga lettingae TMO来源的糖苷水解酶(Sequence ID:YP_001471199.1)同源性最高,为71%。重组转化子经诱导所得酶最适反应温度为55℃,最适pH值为7.5,酶液经58℃热处理30min,酶活残留65%以上,该酶能将乳糖或豆粕中的乳糖水解为半乳糖和葡萄糖。

This study mainly focused on the cloning and expression of a β-galactosidase gene isolated from the hot springs metagenome and its primary application in animal nutrition. β-galactosidase gene was amplified by using metagenomic DNA isolated from a hot spring with a temperature of 65 ℃ in Eryuan in Dali as a template. Sequence analysis result showed that the sequence potentially encoded a β-galactosidase,since the encoded amino aicd shared 71%sequence homology with that of Thermotoga lettingae TMO glycoside hydrolase. After heterologous expression in E. coli Rosetta and affinity purification,the purified product was further subjected to analysis of enzymatic characteristics.The results showed that the optimum acting temperature and pH value of the expressed β-galactosidase were 55℃ and7. 5,respectively. The crude lysate kept about 65% of its enzyme activity after treated at 58 ℃ for 30 min. The β-galactosidase could hydrolyze lactose in soybean into galactose and glucose,indicating a good application prospect in feed production.